Servo-assisted mechanical transmissions, which are structurally similar to a manual mechanical transmission of the traditional type except for the clutch pedal and the gear selection lever operated by the driver being replaced by corresponding electric or hydraulic servo-controls, are increasingly widespread. By using a servo-assisted mechanical transmission, the driver simply needs to send the order to shift gear up or down to a transmission control unit, and the transmission control unit independently shifts gear by acting on both the engine and the servo-controls associated to clutch and gearbox.
A gear shifting order may be generated either manually, i.e. following a command imparted by the driver, or automatically, i.e. regardless of the driver's action. When the gear shifting order is generated, the transmission control unit drives the servo-control of the clutch to open the clutch so as to mechanically separate a primary shaft of the gearbox from a drive shaft; at the same time, the transmission control unit acts on the engine control unit to temporarily reduce the driving torque supplied by the engine itself.
Once the transmission control unit has verified the opening of the clutch, the transmission control unit drives the gearbox servo-control to disengage the currently engaged gear; when the transmission control unit has verified the gear disengagement, the transmission control unit drives the gearbox servo-control to displace the gearbox control shaft so as to arrange the engagement of the new gear. Once the transmission control unit has verified that the gearbox control shaft has reached the desired position, the transmission control unit drives the gearbox servo-control to engage the new gear.
Finally, when the transmission control unit has verified that the new gear has been engaged, the transmission control unit drives the clutch servo-control to close the clutch, so as to make the primary shaft of the gearbox and the drive shaft reciprocally and angularly integral; at the same time, the transmission control unit acts on the engine control unit to restore the driving torque supplied by the engine itself.
The clutch servo-control is generally of the hydraulic type and comprises a single hydraulic actuator for displacing the clutch from the closed position to the open position and vice versa. Generally, the gearbox servo-control is also of the hydraulic type and acts on a gearbox control shaft to impart to the control shaft itself both an axial displacement, i.e. along a central axis, to select the gear range, and a rotation about the central axis to engage and disengage each gear. Consequently, the gearbox servo-control comprises a first hydraulic actuator mechanically coupled to the control shaft to axially displace the control shaft and a second hydraulic actuator mechanically coupled to the control shaft to rotate the control shaft.
The actuation system of the servo-assisted mechanical gearbox generally consists of four assemblies (control fluid reservoir, electric pump for pressurizing the control fluid, solenoid valve assembly, hydraulic actuator assembly) which are reciprocally connected and thus filled with the control fluid by the actuation system manufacturer. Once the actuation system has been completed (i.e. once the assemblies of the actuation system have been reciprocally connected and filled with the control fluid), the manufacturer of the actuation system sends the actuation system itself to the mechanical gearbox manufacturer who mounts the actuation system in the mechanical gearbox.
Currently, during the transportation of the actuation system, the assemblies of the actuation system themselves are fixed to a rigid transportation bracket (which may be disposable or returnable) having a flat shape to optimize the volumes. The transportation bracket is used also when assembling the actuation system in the mechanical gearbox; specifically, assembling the actuation system in the mechanical gearbox contemplates fixing the solenoid valve assembly to the mechanical gearbox in its definitive position leaving the solenoid valve assembly mounted on the transportation bracket. Subsequently, the transportation bracket must be removed because its presence prevents the access to some parts of the mechanical gearbox where the reservoir is fixed; being the reservoir connected in a non-detachable manner to the solenoid valve assembly, the reservoir must be disassembled before being able to remove the transportation bracket. However, such operation is complicated and requires the intervention of at least two operators: one operator to hold the reservoir after it has been disassembled from the transportation bracket, and another operator to remove the transportation bracket and to mount the parts of the mechanical gearbox where the reservoir is fixed. In other words, when assembling the actuation system in the mechanical gearbox, the transportation bracket hinders the freedom of movement of the operator and must therefore be removed during an initial step of mounting; however, the removal of the transportation bracket in an initial step of assembling makes the handling of the actuation system assemblies complicated (particularly that of the reservoir) and thus the intervention of two operators is required, at least for a certain time, with an evident increase of cycle times and assembling costs.